The proposed project is a renewal of "High Risk Crack Use Settings and HIV in El Salvador" and builds on a successful research collaboration between the Center for AIDS Intervention Research (CAIR), the Universidad Centroamericana Jos[unreadable] Sime[unreadable]n Ca[unreadable]as (UCA) and the Fundaci[unreadable]n Antidrogas de El Salvador (FUNDASALVA) to test a multi-level community-based intervention developed in the parent project in collaboration with community residents, crack users, and the Ministry of Public Health and Social Services. Project Encuentro consists of provision of social network HIV testing and Peer Network Interventions among crack users. Specific aims of the proposed research are: (1) To measure the effectiveness of the multi-level community-based intervention with regard to increasing testing rates and decreasing sexual risk behavior among crack users;(2) To analyze the combined effects of the Peer Network and social network HIV testing components on increases in testing and reductions in sexual risk behavior among crack users;(3)To explore the community and organizational factors of successful or unsuccessful implementation (systems level analysis) of various components of the multi-level, community-based HIV prevention intervention. To accomplish these aims we will use a mixed qualitative, quantitative approach. In order to explore aims 1 and 2, we will conduct cross-sectional surveys with crack users residing, buying or using crack in each of the 4 community sites (n=300 per assessment) and measure HIV testing rates in MSPAS clinics before and after implementation of the social network HIV testing. Implementation of the intervention components will be rolled out consecutively, and we will administer multiple assessments (6 total, including 2 baselines) in order to assess trends in increasing effects of the intervention components over time. We will also carefully measure exposure to non-Encuentro HIV prevention interventions and information, to further rule out historical change unrelated to our intervention. To explore aim 3, we will conduct semi-structured interviews with community partners, and observations of trainings, community meetings and steering committee meetings. To examine fidelity and quality of intervention components, we also will collect observations of HIV testing, and sessions of the Peer Network Intervention with crack users. Data for Specific Aim 3 will be collected throughout the project. Results from key informant interviews and observations will be coded to reflect key systems factors related to successful implementation of intervention components in the four community sites. Coded barriers and facilitators will then be included as data in the cross-section surveys for each community, corresponding to the same time periods of intervention implementations and field observation or interviews. PUBLIC HEALTH RELEVANCE: This study is significant in that it will provide a comprehensive, holistic evaluation of a multi-level community based HIV prevention intervention delivered to a high-risk population in a relatively neglected region of the world. We will assess intervention impact on community capacity, the reach and intensity of the intervention, and population level behavior change among crack users. Because we will carefully evaluate community and organizational level factors that may impact implementation, this project will provide important information about the translation, scale up, and sustainability of evidence-based interventions into real world settings.